This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The smooth green snake, Opheodrys vernalis, is found across the northeastern United States and southeastern Canada, and in 24 isolated populations in the Great Plains and Rocky Mountains. The latter populations are apparently small and may be in danger of local extinction. Within South Dakota, two populations are known, one in the southeastern corner of the state and one in the Black Hills. In addition, one population is found in the Bear Lodge Mountains of Wyoming, less than 50 km from the Black Hills. Additionally, the later two populations seem to be two of the densest populations of O. vernalis known. We are investigating genetic variation amongst the two South Dakota populations, the Bear Lodge Mountains population, and a reference population in New Mexico. The snake may be of conservation interest, especially if genetic variation is substantial amongst populations. Our study is a first step towards understanding differentiation amongst populations of O. vernalis in the United States.